after submitting email i want to send mail to manager but same email is going 2 times to manager
It won’t happen 
because I did the test yesterday, so I didn’t see any such problem. When you submit, check the email queue, how many emails are there? And how many times does the mail go into the email queue? Check it out.
from email only i verified and i made myself manager and i tested it from employee so email is coming to me 2 times